Development trend, evolution of themes, gaps, and challenges of the research investigating ozone effects on vegetation

Tropospheric ozone (O3) is a potent oxidant that can harm plants, making it a key focus of research in ecology and agriculture. However, comprehensive reviews about the developmental history of O3 research on plants are lacking. This review utilized Citespace software to unveil the evolution of the main research themes over time, which correlated with three distinct developmental periods. During the first period, researchers primarily focused on the impact of O3 on photosynthesis and plant defense responses. As time progressed, more in-depth investigations were undertaken, including determining the critical levels at which O3 damage to plants occurred, analyzing the source–sink carbon balance and carbon allocation, assessing food security based on risk evaluation, identifying quantitative trait loci associated with O3 tolerance, conducting transgenic research, and exploring the combined effect of multiple stressors on vegetation within the context of climate change. Despite these insights, several gaps and challenges remain, that merit future considerations. Greater research efforts should focus on (1) insufficient studies on the combined effects of O3, CO2, and drought in the context of global warming; (2) intermittent elevated O3 events and plant recovery mechanisms under low O3 concentration; (3) reproductive and renewal capacity of species, and t O3 effects on community stability or composition; (4) updating O3 flux measurements to reflect effective O3 flux when O3 index is applied, and challenges in determining species-specific phytotoxicity threshold; and (5) O3-tolerance gene screening and breeding.